Towards Control of Magnetic Fluids in Patients: Directing Therapeutic Nanoparticles to Disease Locations

This article describes a range of results, from passive magnet design to optimal feedback control of a distributed ferrofluid. Representing magnetic forces as the gradient of a magnetic energy allowed design and demonstration, in animal experiments, of a simple open-loop two-magnet system to inject nanoparticles into the inner ear. Then a petri-dish test bed was used to develop and test optimal closed-loop manipulation of a single ferrofluid droplet.The demonstrated algorithms exploited the quadratic dependence of the magnetic forces on control inputs while accounting for magnet time delays and spatial discontinuities in the optimal control. All dimensional parameters were reduced to three essential nondimensional numbers, and ferrofluid behavior was mapped across the entire feasible drug delivery parameter space.